Is it possible to walk in a frictionless world. I think you won't be able to walk because walking depends on friction acting on your feet. I think about it like an ice rink because when you try to walk on an ice rink it is incredibly hard as there is less friction acting on your feet. Can it be shown mathematically using principles of mechanics that it is not possible to walk in a frictionless world, or is it only by experiment?
Edit: I do not mean outer space by frictionless world, because you are not being pushed on a surface by gravity. I am looking for a mechanism that would allow a biological specimen to walk on a surface without friction, assuming that all other laws and effects are in place.
Edit: What I mean by walking is that you must move your legs in order to walk. I read the idea about using cleat like shoes to walk. The cleats would make holes into the ground allowing something to push off of horizontally allowing you to walk, but how would that even work? If the world is frictionless making holes in the ground would just turn the material you are standing on into rubble. The rubble would then act like the original material that you wanted to put holes into in the first place. How does material stay together in a frictionless world?
Answer
Although friction is not one of the four basic forces of nature, it exists because those basic forces exist. Friction is the resistance to motion of two objects held against each other.
Friction that allows us to walk depends on gravity to convert our mass to weight which holds our feet against the surface where static friction enables the soles of our shoes to push off against the surface of the Earth.
Even when ice skating, kinetic friction keeps the blades sliding against the ice in a forward direction, and static friction allows the skates to push off to propel the skater forward.
Some friction is caused by molecular attraction, such as when Vibram soles are able to maintain grip on smooth rock. This is the result of electromagnetic forces in the rubber molecules of Vibram attracting rock molecules.
Even a rocket engine, which otherwise could be used to propel you in a frictionless environment, depends on the difference in force between friction caused by great pressure of propellant exhaust on a small area (exit pressure) and the lesser friction of propellant exhaust flowing through a larger area (free stream pressure). The equation for rocket thrust shows this:
$$\text{rocket thrust} = \text{mass flow rate} \times \text{exit velocity} + (\text{exit pressure} - \text{free stream pressure}) \times \text{exit area}$$
The coefficient of friction is a measure of how strongly two surfaces will stick together. It's the ratio between the force necessary to induce sliding, and the pressure holding the two surfaces together. It can be used to calculate the amount of friction:
$$F = u \times N$$
$F$ is the frictional force
$u$ is the coefficient of friction
$N$ is the normal force (perpendicular to both surfaces, which presses them together)
If surfaces could slide with no force at all, the numerator of their coefficient of friction would be zero, the coefficient itself would be zero, and the frictional force between those two surfaces would be zero. Here is a list of coefficients of friction of various materials. The maximum coefficient of friction is one, and the minimum is zero.
Friction exists everywhere in the Universe. To have no friction, there would have to be no gravity, no electromagnetic force, no gluons to hold atomic nuclei together, and no bosons to allow the buildup of heavy nuclei in stars. All would be chaos. Newton's third law would be inoperative. The universe would be a soup of uniform density with no structure. Entropy would tend to be maximal. You would not be able to walk.
No comments:
Post a Comment